1. Field of the Invention
The present invention relates to cutting and shredding devices, and, more particularly, to shredding devices designed for the destruction of microfilm and similar information carriers carrying microimage impressions.
2. Description of the Prior Art
In recent years, microfilm has come into increasing use as a microimage data carrier for the long-term storage of a great variety of information. Most commonly, these microfilm data carriers take the shape of film reels, film sheets, so-called microfiches, or microfilm sections which form a part of punched cards. The information which is stored on microfilm is of a permanent nature and cannot be erased, should it become obsolete. In the case of microfilm information of a confidential or proprietary nature which has become obsolete, or otherwise requires destruction, the destruction of the microimage data can only be accomplished by destroying the data carrier itself.
While one might assume that microfilm can be shredded in much the same way as paper is being shredded, it has been found that paper shredders are generally unsuitable for the destruction of microfilm, even if they are capable of cutting the much tougher film stock. More importantly, however, the size of the shreds produced by paper cutters is much too large for a safe destruction of the microimage information involved, considering the greatly reduced scale on which this information is registered on the microfilm carrier.
Known document shredders, as a rule, cut each sheet of paper into a large number of narrow longitudinal strips, as the sheet is fed between rotary cutters. For technical reasons, it is not possible to modify these cutters so that they form an arrangement of sufficiently compact and closely spaced dimensions that would enable them to effectively destroy microfilm.
A further shortcoming of these prior art devices lies in the uninterrupted working contact between the shredding cutters and the material to be shredded. This means that, because of the inevitable generation of friction, the shredding cutters build up heat which is transferred to the material to be shredded, with the result that the latter softens and develops a tendency to pack together, including the possibility of becoming bonded to the cutters.
Large-capacity shredder installations which are designed for the destruction of office materials of all kinds, including the shredding of entire file folders, are generally too bulky and also too costly for most applications. Also, these high-powered installations produce a shredded waste whose particles are still too large to be acceptable for the purpose of destroying microfilm data carriers.
The thermal destruction of microfilm data carriers is not practical, due to the move away from flammable film stock to nonflammable safety film stock. Increasingly, the material used for microfilm is a highly resistant film strip of polyester which is so resistant to tearing and cutting that the above-mentioned known shredding devices are simply incapable of cutting it. In many instances, therefore, where information could be advantageously stored on microfilm, such storage is foregone, because of the inability of effectively destroying the microfilm data, when they are obsolete.